Can bacteria survive in a blender?

Does raw dough cause stomach ache?

For many, when baking cakes or biscuits, snacking on the raw dough and licking it out of the mixing bowl is simply part of it. But does raw dough really cause stomach ache, as many claim? And is it true that it can even be harmful to your health? The BESSERwisser investigated this question.

Microorganisms in the raw dough

The raw mass of cakes and biscuits tastes good, there is no doubt about that. Who doesn't like to taste the freshly stirred dough full of anticipation? The leavening agents contained in it, which are supposed to make the dough loose and airy, can cause unrest in the digestive tract. Yeast eaten raw continues to ferment in the stomach, and baking soda also continues to produce carbon dioxide in the stomach. Gas can accumulate in the gastrointestinal tract and cause abdominal pain and flatulence. Baking mass usually also contains flour and eggs, which are a potential health hazard when raw: They can contain harmful microorganisms that are only killed when baking. This applies not only to cookies and cakes, but also to pizza and bread dough, for example.

Flour as a source of danger

The American Food and Drug Administration (FDA) has long warned against tasting raw dough. In its raw form, flour is suspected due to the contamination it contains from the bacterium Escherichia coli Cause diseases. In 2017, this was confirmed by an American study in which reported E. coli-Infections were examined more closely: Almost 40 percent of them could be traced back to the consumption of raw flour. [1] The affected flour manufacturers then had to withdraw their products from the shelves. In Austria, however, no cases of illness due to contaminated flour have yet been reported.

Escherichia coli

At Escherichia coli it is rod-shaped, gram-negative bacteria. These were first isolated from the large intestine (colon) of small children by the pediatrician Theodor Escherich in 1885.E. coli multiply best between 10 and 47 ° C and occur in human and animal intestines. These microorganisms are part of the natural intestinal flora and are usually harmless. They only make you sick if they are carried away from the intestine to other parts of the body, where they can cause symptoms such as urinary tract infections, peritonitis or gallbladder inflammation [2].

But there are also certain strains of E. colithat can be harmful to health. These include thoseE. coli Bacteria that produce a certain toxin called vero or shiga toxin. These bacteria are called VTEC (Verotoxin Forming E. coli) or STEC (Shigatoxin Forming E. coli) known. Their toxins have a harmful effect on humans and can cause abdominal pain, vomiting, fever, diarrhea and, in the worst case, even kidney failure [2, 3]. By boiling, baking or frying at over 70 ° C you can E. coli Bacteria are killed [3].

How do microorganisms get into the flour?

Flour serves as a raw, minimally processed product that should be blended with other ingredients and heated before consumption. It contains hardly any water per se and normally does not encourage bacterial growth. However, it has been shown that microorganisms can survive on wheat and other flour components, since grain is not treated against bacteria. Animal excretions and pathogenic germs that contaminate the grain can be processed further with the flour.

Eggs are a source of danger

The fact that raw eggs can be contaminated with salmonella is well known. These pathogens are mainly found on the shell of eggs and are rarely found in eggs themselves.


Salmonella is a genus of rod-shaped bacteria that belongs to the group of enterobacteria. Some species of salmonella can cause serious illnesses in humans; these are commonly referred to as salmonellosis.

With a Salmonella infection, the symptoms usually appear six to 72 hours after the infection - mostly depending on the number of pathogens that have entered the body. If the salmonella in the intestinal mucous membrane of the small intestine release their toxic metabolic products, typical symptoms such as nausea, vomiting, abdominal cramps, diarrhea and headaches can occur, and fever can also occur. If the bacteria get into the bloodstream, they can cause complications in organs outside the intestine and cause severe disease, which is rare. Salmonella infection usually occurs through contaminated food. [4]

Salmonella multiply at temperatures between seven and 45 ° C. Moisture favors their growth, and the pathogens are only killed at temperatures above 75 ° C. They can even survive in freezers at minus 20 ° C. The best way to avoid salmonella infections is to use the freshest possible food and good kitchen hygiene.


Snacking on raw dough can actually cause abdominal pain and gas, as the leavening agents it contains can cause gases to build up in the gastrointestinal tract. However, this depends on how much of the raw mixture was consumed and how sensitive the sweet tooth reacts.

The likelihood of getting an infection through the raw dough of cakes, biscuits, pizza, or bread E. coli-Bacteria or with Salmonella is in principle possible, but it is very low. At least there have been no cases of this kind in Austria so far. But if you want to be on the safe side, it's better to try the raw dough. The fully baked end product does not pose any risk in this regard, as the pathogens are killed by baking.


[1] Crowe SJ, Bottichio L., Shade LN Shiga Toxin – Producing E. coli Infections Associated with Flour (2017). N Engl J Med 2017; November 23, 377: 2036-2043: doi: 10.1056 / NEJMoa1615910

[2] Austrian Food Safety Agency (AGES): Escherichia coli including verotoxin-producing E. coli (VTEC) (2020)

[3] Statement by the Federal Institute for Risk Assessment: Shiga toxin-producing E. coli in food: Prediction of the disease-causing potential of the various strains is not yet possible. DOI 10.17590 / 20180419-133502

[4] Austrian Food Safety Agency (AGES): Salmonella.

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